depends: fix Boost 1.55 build on GCC 5 #6280

Boost assumes variadic templates are always available in GCC 4.4+, but they aren't since we don't build with -std=c++11.

This applies the patch that fixed the issue in boost 1.57: https://github.com/boostorg/config/commit/eec808554936ae068b23df07ab54d4dc6302a695

See also: https://svn.boost.org/trac/boost/ticket/10500

(Or we could just bump the Boost version... I dunno how risky that is, so this is the conservative fix.)

NACK, we shouldn't be patching dependencies here since we need to support building with system dependencies too. Doesn't gitian already succeed? That's all that should use depends/ ...

At least for 0.12/master I think we should boost the boost version instead of piling up more local patches.

For backporting this seems fine to me.

@luke-jr the depends system does not only exist for gitian, it's also there for doing cross-compilation, or building when the necessary dependencies don't exist for the distro. Unfortunately it doesn't contain a gcc version, so it has to work with user's gcc which comes from a wider version range than just that used by gitian.

To be clear, this isn't a failure to build Bitcoin with system dependencies, it's a failure to build Boost. My own need was for working on the depends build itself (namely bumping Qt) without going through the whole gitian setup. I didn't see this as the common case which is why I didn't base against 0.11. The gitian environment will be affected too if it's ever updated. Feel free to close if bumping Boost is the preferred way to go; I just wanted to make the problem and one solution known.

Agreed with bumping boost. There were problems with some versions after 1.55, but iirc 1.58 is relatively solid and a good candidate for us.

@theuni Also bump boost for releases? We could use this as a more minimal patch on 0.11 branch before the next rc.

@laanwj I meant for master. This looks good for 0.11, I think it's a bit late for such a big bump there.

OK. Going ahead and merging this then, we can remove the patch again when the bump happens.